Primary Amine-Functionalized Chiral Covalent Organic Framework Enables High-Efficiency Asymmetric Catalysis in Water

Area of Science:

• Materials Science
• Organic Chemistry
• Catalysis

Background:

• Aqueous asymmetric catalysis using chiral covalent organic frameworks (COFs) is an emerging field with significant potential.
• Developing efficient and selective catalysts for reactions in water is crucial for green chemistry.

Purpose of the Study:

• To present the first example of aqueous asymmetric catalysis using a primary amine-tagged chiral COF.
• To investigate the catalytic activity and enantioselectivity of the novel COF in an asymmetric aldol reaction conducted entirely in water.

Main Methods:

• Synthesis of a primary amine-tagged chiral COF (D-ADP-TAPB COF) via postsynthetic deprotection.
• Characterization of the COF's morphology and functional groups.
• Application of the COF as a catalyst in the asymmetric aldol reaction between cyclohexanone and 4-nitrobenzaldehyde in water.

Main Results:

• The synthesized D-ADP-TAPB COF exhibited uniform spherical morphology with well-distributed chiral primary amines.
• The COF catalyzed the aqueous asymmetric aldol reaction with high yields (up to 90%) and enantiomeric excess (ee, up to 85%).
• This represents the first chiral COF catalyst achieving high performance for this reaction solely in water.

Conclusions:

• The D-ADP-TAPB COF is a highly active and enantioselective catalyst for aqueous asymmetric aldol reactions.
• This work expands the design of chiral COFs for asymmetric catalysis and promotes green, water-based enantioselective synthesis.
• A plausible reaction mechanism was elucidated, providing insights into the catalytic process.